Add to header and Header Nav

Hi I am working on terrafirma2 theme, the website I am working on ishttp://labergerie.convivoo.org/... . The issue is when I go to editing of this page I don;t see Add to header and Header Nav so I can add block there. I want to add internationalization flags on the top right header area. I am able to add flags on the sidebar but on the top not header nav coming nor Add to header.

Do I have add some in the code file, please suggest me links that will help me further progress on my website. Thanks, Chander.